We investigate accretion flows onto supermassive binary black holes (SMBBHs) from a circumbinary disk with and equal-mass, eccentric binary on subparsec scales, using a Smoothed Particle Hydrodynamics (SPH) code. We find that the material can be supplied from the circumbinary disk, which leads to the formation of two accretion disks around the SMBBHs. The mass accretion rates are significantly modulated with the binary orbital motion. These could provide an observable diagnostic of the existence of SMBBHs (e.g., OJ 287) on subparsec scales in merged galactic nuclei.